(1) Field of the Invention
The present invention relates to structures used for containing and conveying molten metal, and to parts of such structures. More particularly, the invention relates to such structures having a refractory or ceramic vessel contained within an outer metal casing used to support, protect and, if necessary, align the refractory vessel.
(2) Description of the Related Art
Metal containment structures of this kind generally include a refractory vessel of some kind, e.g. a molten metal conveying vessel, held within an outer metal casing. The vessel may become extremely hot (e.g. to a temperature of 700° C. to 750° C.) as the molten metal is held within or conveyed through the vessel. If this heat is transferred to the outer metal casing of the containment structure, the metal casing may be subjected to expansion, warping and distortion and (if the vessel is made in sections) may cause gaps to form between the sections of the vessel, thereby allowing molten metal leakage. Additionally, the outer surface of the casing may assume an operating temperature that is unsafe for operators of the equipment. These disadvantages are made worse if additional heating is applied to the vessel to maintain a desired temperature for the molten metal. For example, temperatures of up to 900° C. may be present at the outside of the vessel when vessel heating is employed. Layers of insulation may be provided between the vessel and the interior of the casing, but such layers may not provide rigid support for the vessel and may not make it possible for a gap to be formed between the vessel and the casing for heat circulation when a heated vessel is required.
To overcome such problems, the vessel may be rigidly supported at various spaced positions within the interior of the metal casing, thereby permitting the formation of a thermal isolation gap between the vessel and the casing. Such a gap also allows for heat circulation in distribution systems that apply heat to the vessel. Layers of insulation may then be used to line the interior of the casing on the casing side of the gap to provide further thermal isolation for the metal casing. However, rigid supports cannot accommodate the thermal expansion and shrinkage that the vessel experiences during thermal cycling of the distribution system, and tend not to contain cracks that may form in the vessel.
There is, accordingly, a need for improved means of providing rigid support for a ceramic vessel within a metal casing of a metal distribution structure.